1. Technical Field
The present invention relates to a motor.
2. Description of the Related Art
Spindle motors are commonly used in electronic products, for example, computer drives, which require accurately-rotating devices. Such spindle motors are extremely promising because the spindle motors can be rotated at a high speed with less power and can be readily controlled with high precision.
A typical spindle motor is constituted by a rotating rotor and a stator, which supports the rotating movement of the rotor.
However, a whirling effect may occur when the rotor rotates because of a gap formed between the rotational axis of the rotor and the through-hole of the stator supporting the rotor.
A useful method known to prevent such whirling effect from occurring is forming an asymmetric gravitational force, i.e., an asymmetric preload, between the rotor and the stator. As such, a method of forming an asymmetric magnetic force by disposing an asymmetric magnetic member on the rotational axis of the stator has been proposed. With the spindle motors becoming thinner, however, the drawback to such method is that it is difficult to form a space for installing the magnetic member inside the stator.
Even though a method of disposing a magnetic member asymmetrically on the rotor has been also proposed to form an asymmetric preload, the magnetic member asymmetrically disposed on the rotor has caused an uneven distribution of load, resulting in undesired vibration when the rotor rotates.